Question

A man takes 20 seconds to climb 5m up a ladder. He weighs 720N. Calculate the power he must deliver to do this.

Answer 1

Answer:

180 W

Explanation:

The work done by the man against gravity is equal to its gain in gravitational potential energy:

$W=mg\Delta h$

where

(mg) = 720 N is the weight of the man

$\Delta h= 5 m$ is the change in height

Substituting,

$W=(720)(5)=3600 J$

The power he must deliver is given by

$P=\frac{W}{t}$

where

W = 3600 J

t = 20 s is the time taken

Substituting,

$P=\frac{3600}{20}=180 W$